(1) Field of the Invention
This invention relates generally to position determination and relates more particularly to methods and apparatus for determining the position of objects, which are located indoors or, outdoors in confined areas.
(2) Description of the Prior Art
A fast determination of the location of devices, objects, or machine is a difficult task, e.g. for the location of a nearest medical diagnostic device in a hospital or for the location of a moving device as e.g. a fork lifter or a robot in a big ware houses, etc. The requirements of accuracy vary for these different applications in the order of magnitude between 10 meter and less than 1 meter.
It is a challenge for the designers of systems for position determination to achieve low-cost systems having the accuracy required. There are known patents in the area of position determination.
U.S. Pat. No. (US 5,525,967 to Azizi et al.) proposes a system and method to monitor the specific location of a person, pet or item of personal property by employing elements that enable the user to pinpoint both the distance and the direction of the person or object being monitored relative to the position of the monitoring or transmission unit (the “source”), comprising a tracking transceiver unit, which tracks and monitors the person or object, and the target transceiver unit, which is worn or affixed to the person or object being monitored. The tracking transceiver unit broadcasts a signal to a target transceiver unit, which, upon receiving the signal, will then broadcast a response signal back to the tracking transceiver unit. The tracking transceiver unit's antenna, which comprises a plurality of flat sensor plate-like elements formed together in a generally spherical configuration, picks up the signal and then conveys the information it receives to a special response signal processor unit, which analyzes the data to determine the direction of the person or object being monitored. Information filtered and analyzed through the response signal processor unit is then conveyed to a central processor unit, which uses the data to calculate the distance of the person or object being monitored from the source.
U.S. Pat. No. (4,868,544 to Havens) discloses a shopping cart retrieval system being designed to allow search teams to detect and recover stolen or misplaced shopping carts. It consists of two distinct units of electronic equipment integrated together to form a retrieval system. The heart of the system is a VHF “beacon” radio transmitter implanted in the handle of the shopping cart which is continuously emitting a signal when it leaves the store. A search team, assigned the task of locating and recovering shopping carts, is equipped with a VHF radio receiver with both omni-directional antenna for detection of a shopping cart at maximum range, and a directional antenna used for the close-in location process.
U.S. Patent Application Publication (US 2005/0192027 to Kim et al.) discloses an apparatus for determining position information of one or more UEs (User Equipments), which includes a plurality of Node Bs for transmitting propagation signals to UEs positioned in a specific cell, and generating predetermined data for measuring position information of the UEs on the basis of propagation signals received from the UEs; a GPS (Global Positioning System) auxiliary information manager for generating and storing GPS auxiliary information associated with a specific cell using a GPS satellite signal received via a built-in GPS receiver; and a RNC (Radio Network Controller) connected to the plurality of Node Bs, for receiving GPS auxiliary information from the GPS auxiliary information manager in response to a request signal of at least one Node B from among the plurality of Node Bs, optimizing the received GPS auxiliary information for every Node B, selecting the optimized GPS auxiliary information, and periodically transmitting the selected GPS auxiliary information to the UEs using a multicast method, in which the Node Bs broadcast the GPS auxiliary information received from the RNC to the UEs positioned in a corresponding cell over a broadcast channel. The apparatus uses a multicast method to differently transmit individual GPS auxiliary information needed for different cells, so that transmission efficiency increases and UEs can more quickly determine their positions.